Processes of cross-linking polymers can involve the use of cure systems comprising various cross-linking agents, accelerators, and acid acceptors. The agents perform the actual cross-linking, the accelerators increase the rate of cross-linking, and the acid acceptors scavenge ions resulting from the cross-linking reaction thereby enhancing accelerator performance.
A cure system used in cross-linking halogen-containing polymers that uses as its major components ethylene thiourea as a cross-linking agent, and red lead (Pb.sub.3 O.sub.4) as an accelerator is known in the art. This system yields stable vulcanizates possessing good physical properties. However, red lead is toxic, and, therefore, a cure system without red lead is preferable.
Cure systems using polyoxyethylene compounds as cross-linking agents with thiuram sulfides, particularly tetramethylthiuram disulfide, as accelerators and metal compounds, particularly magnesium oxide, as acid acceptors has been reported in Japanese Patent OSAKA SODA KK 18.02.82-JP-025626. However, a cure system that uses only a thiuram sulfide, such as tetramethylthiuram disulfide, and a metal compound, such as magnesium oxide, cures a halogen-containing polymer slowly and results in a vulcanizate with non-advantageous properties, e.g., low modulus and low elongation.